The present invention relates to carding machines with a main cylinder, lickerin and doffer, comprising self-cleaning stationary flats with dust and trash extracting units in the main carding zone.
Conventional carding machines use revolving flats that move around the peripheral surface of the upper part of the carding cylinder. Revolving flats are in general use for cotton carding because their flats can be cleaned when they are not opposing the surface of the carding cylinder.
Cards equipped with revolving flats suffer from several disadvantages:
Only a small number of the revolving flats is in the working zone. The revolving flats have only a temporary carding function as long as they pass over the working zone. The bigger part of the revolving flats is permanently not in a carding function. Therefore, the revolving flat card needs a large number of flats that are ineffectively used, cause higher costs and do not contribute to the carding effect. PA1 During their passage on the surface of the carding cylinder the clothings of the revolving flats become loaded with extracted material. For a large part of the working cycle therefore the carding efficiency of the revolving flats is considerably reduced or even ineffective. PA1 Each of the flats of the revolving card passes over the whole main carding zone and does not stay at a specific position. Therefore, all the flat clothings have to be identical to obtain a regular carding effect. A better carding effect is obtained with rougher flat clothings at the beginning and with finer flat clothings toward the end of the main carding zone, which is not possible with revolving flats. PA1 The bars of the revolving flats drag continually on the flexible bend, which guides the flats in the desired distance to the surface of the cylinder. The flexible bend, an important and expensive part of the revolving flat card, and the flats themselves suffer from considerable wear and tear which causes high maintenance costs. PA1 The revolving flat card requires a complicated construction for driving, guiding and cleaning which induces high costs for manufacturing and maintaining this type of card. PA1 The additional elements do not remove the technological and mechanical disadvantages of the revolving flats in the main carding zone except that they subsequently compensate partially for their imperfect carding effect. PA1 Those additional elements further complicate the construction of the card and increase its manufacturing and maintaining costs. PA1 Cards with stationary flats are built without moving parts in the main carding zone beside the main cylinder. A simple general design and construction are therefore possible, which results in lower manufacturing and maintaining costs. PA1 All the stationary flats are permanently active in the working zone. Therefore, fewer flats are needed in comparison to the revolving flat card. All the flats can be permanently used. PA1 There is no motion of the bars of the stationary flats on the flexible bend, therefore wear and tear of those elements are avoided. PA1 No supplementary flat cleaning devices outside the main carding zone are necessary. PA1 The flat position relative to the main cylinder can be individually set, thus additionally optimising the carding quality.
These above described disadvantages gain importance when higher card productions are maintained.
Several attempts have been undertaken to overcome these described disadvantages of the revolving flat card, the most important are the following:
One of those attempts consists in improving the incomplete carding effect of the revolving flats by installing supplementary dust and trash removing devices on the cylinder surface outside the main carding zone. The major disadvantages of such approaches are:
Another attempt to overcome the disadvantages of the revolving flat card consists in more radical solutions that replace the revolving flats by stationary flats. Stationary flats entirely replace their revolving counterparts, they are rigidly fixed to the main frame around a portion of the main cylinder and they do not move.
Stationary flat cards have some major advantages:
The flat clothings can be adjusted to their position in the main carding zone. Rougher clothing's might be positioned at the beginning and finer clothings toward the end of the main carding zone.
Several approaches have been proposed to construct a stationary flat card, but each with some more or less severe disadvantages:
U.S. Pat. No. 2,879,549 (1957) herein incoperated by reference uses a flexible bend to adjust the distance of the stationary flats to the cylinder surface. No extraction or cleaning devices are described. The stationary flats are not equipped with any wiring, clothing or such. A card like that will not result in sufficient carding quality of the passing staple fibres. Self-cleaning of the flats is claimed by the card wind in the sealed chamber of the whole main carding zone and by the replacement of the steel wire clothing of the flats with a non-loading, rigid, abrasive granular surface. No supply air from outside the card is used. As claimed, the extracted material has to pass under high pressure through the entire main carding zone. The state of the art is a flat clothing of steel wire or hooks, which is proven as inevitable for proper carding performance. The prescribed design severely impairs with the carding effect and therefore could not gain any attention in mill practice.
JP-A-58-163731 A (1983) uses stationary flats fixed at a chain and on the flexible bend. Mote knife-like projections at the side of the flats and side clips, forming dust-sucking ducts, are used to separate dust, trash and short fibres and to remove them by the card wind after each flat. The details of design are not further specified. The main disadvantages of this solution are: no supply air from the outside of the carding zone is used, so that the exhaust air is not compensated. This induces distortion of the card wind and impairing the carding effect of following flats. The mote knife and the suction duct of separate attached parts at each flat require a complicated construction. The separate adjustment of the mote knifes of each flat is laborious and therefore impracticable for the use in mills.
WO-A-89/00214 (1989) describes a waste removing device after the main carding zone of a revolving flat card, a mote knife, an air guiding plate, a sharp edge and supply air from outside the card together with the card wind to extract and remove remaining waste and short fibres from the cylinder surface. This solution uses a self-regulating air-stream with supply air and exhaust air. Being positioned after the main carding zone, it can work as extraction device neither for revolving nor for stationary flat clothings in the main carding zone. Being positioned after the main carding zone the device has no significance to the carding effect in the main carding zone. The design and shape of this extracting device make it non-applicable between flats in the main carding zone.
U.S. Pat. No. 5,530,994 (1996) primarily claims a blade for trash removal with a rounded edge of a radius greater than 1 millimetre. Specially designed and shaped flats are shown, which differ from standard flat design. Extraction and removal devices between two stationary flats are shown. The exhaust air with the extracted dust, trash and fibres is removed laterally at one side of the extraction device, which requires eventually a pneumatic suction device. Each stationary flat is fixed directly to the main frame. The separate parts of the extraction device have to be adjusted individually for every flat which needs time and causes high adjustment costs.
The straight blade for the mote knife together with the rounded edge does not give the optimum extraction effect as tests show.
Supply air and exhaust air has to be regulated by adjustment means. The removal of the extracted material at the side of the extracting device might lead to an asymmetric extraction effect and thus should be avoided. The eventual need of a pneumatic suction device causes higher manufacturing and working costs. As each flat is fixed separately at the main frame of the card no common adjustment of the distance of the flats to the cylinder surface is possible.